Metal composites including layer of unwoven wires

ABSTRACT

AN IMPACT RESISTANT COMPOSITE STRUCTURE COMPRISING A NETWORK OF INTERMESHED METALLIC WIRES HAVING YIELD STRENGTH AT LEAST ABOUT 200 K.S.I. DISPOSED BETWEEN AT LEAST TWO SHEETS OR PLATE MEMBERS TO PROVIDE A STRUCTURE HAVING AN EXCELLENT STRENGTH TO WEIGHT RATIO.

Oct. 9,1973 RYE. HOLLIS i 3,764,277

METAL COMPOSITES INCLUDING LAYER 0F UNWOVEN WIRES Filed Aug. 28, 1969 5sheets-sheet 1 22 FIG- 5 FIG-5 L RUSSELL E4 HOLLIS AT l ORN CYS Oct. 9,1973 R. E. HOLLIS 3,764,277

METAL COMPOSITES INCLUDING LAYER OF UNWOVEN WIRES I Filed Aug. 28. 19693 Sheets-Sheet INVENTOR. RUSSELL E. HOLLlS @TM VTM ATTORNFYS Oct. 9,1973 R. E. HOLLIS 3,764,277

METAL coMPosITBs INCLUDING LAYER oF uNwovEN WIRES Filed Aug. 28. 1969 f3 Sheets-Sheet 3 /NVE/VTOI? RUSSELL E. HOLLIS United States Patent O No.853,811 f Int. Cl. E04g 2/00 U.S. Cl. 29191.6 14 Claims ABSTRACT OF THEDISCLOSURE An impact resistant composite structure comprising a networkof intermeshed metallic wires having yield strength at least about 200k.s.i. disposed between at least two sheets or plate members to providea structure having an excellent strength to weight ratio. y

'I'his application is a continuation-impart of application Ser. No.460,309 filed June 1, 1965, now abandoned.

BACKGROUND OF THE INVENTION This invention relates to metal compositesin such forms as sheet, plate, tube or roll which serves as hollowshells for transporting or containing material as coverings, walls,armor, self-sealing casings and reinforcement elements for cloth layers,paper layers and plastic material, all of various shapes, sizes andthicknesses.

There is considerable need in the industrial [field for a composite ormade up structure of metal, asdistinguished from solid metal, which hasa hard and wear resistant surface, resists impact, and still retains theinherent advantage of light weight. From a design and structuralstandpoint, the composite must have a high strength to weight ratio,substantial resistance to compression forces and bullet impact and, incertain forms, can be flexed or bent to shape. Metallurgically, suchmaterials as the mar-aging and alloy steels, precipitation hardenedstainless steels and various titantium alloys have been found suitableas they possess the necessary physical and mechanical properties.However, heretofore the prior art has been unable to get these materialsto respond to the wire drawing and meshing contemplated herein, withoutadversely affecting or weakening the wires.

With this limitation, the prior art had to contend itself in theproduction of screen meshing with the less exotic materials. However,from the discussion to follow, it will be evident that the presentinvention has found a way to overcome the limitation so as to yield acomposite structure not known in the prior art.

SUMMARY FA THE INVENTION The composite structure which forms thepreferred embodiment of this invention is based upon the use of adiagonal truss work between pairs of plates or foils so arranged thatthe effect of any stress applied to the outside plate or foil would beabsorbed as a compressional force on the diagonal members of theinterventing truss work. 'I'he improved composite, which is constructedprimarily of the super-strength metallic alloys having yield strengthsin excess of 200 k.s.i., also takes advantage of the proven premise thattwo plates rigidly separated from one another can withstand a suddenimpact or rupture of one orA both plates much more readily than if thelatter were in contiguous relationship. The spaced plates feature,having the network of wire meshing therebetween, when coupled with theuse of the super-strength metallic alloys gives rise to the highstrength to Weight ratio of this composite.

ice

BRIEF DESCRIPTION oF DRAWINGS FIG. 1 is a perspective view of a typicalcontainer which utilizes the composite structure in the wallconstruction thereof.

FIG. 2 is a sectional view of one embodiment of a composite constructedaccording to the teachings herein.

FIG. 3 is a plan view, with a portion of the upper plate removed toexpose the wires, of the embodiment shown in FIG. 2.

FIG. 4 is a sectional view similar to FIG. 2 but showing a multiplecomposite',

FIG. 5 is a sectional view similar to FIG. 2 but showing a furthermodification thereof.

FIG. 6 is a plan view similar to FIG. 3 but showing the structure ofFIG. 5.

FIG. 7 is a perspective view of a composite structure forming a secondembodiment of this invention.

FIG. 8 is a perspective view of a composite structure showing a thirdembodiment of this invention.

FIG. 9 is a sectional view taken through a curved composite similar tothe composite shown in FIG. 8.

IFIG. 10 is a sectional view similar to FIG. 9 but` DETAILED DESCRIPTIONOF PREFERRED EMBODIMENTS Turning now to a more detailed consideration ofthe invention, it will be observed in FIG.'1 that reference character 1designates a typical 'container whose walls may be constructed from thecomposite to be described herein. Such a container may be used forliquids such as gasoline, oil, which necessitate ruggedness ofconstruction, lightness of weight, and resistance to distortion of shapeand positive leakproofness. As indicated previously, the improvedcomposite described herein is an ideal `material for the wallconstruction of such a container. The wall portions are preferablywelded together by high frequency current at 450,000 c.p.s. applyingrounded metal strips 2 so that no corners are present. Usual inlet andoutlet openings, closed by screw plugs 3, are provided.

One form the improved composite structure may take is shown in FIG. 2.Th'e wire 4 is crimped or bent in a uniform wavy manner and a number ofthese wires are laid in spaced relationship parallel to one another asshown in FIG. 3. While it may not be evident at this point, thisrelationship of the wires should be contrasted fashion, with one setlying on top ofthe other set and receivedjby the rounded troughs of theother set. The best results are obtainable when the longitudinal axis A(FIG. 2) of one bent portion of each wave portion of a wire 4 is at 90with respect to the axis B in they adjacent oppositely bent portion. Asshown in FIG. 2, the curvature at the troughs indicated at 6 is such assnugly to receive the rectilinear wires. For an alternate maximum vstrength in all directions, these wirevforms should best be joined witheach layer at 45 degrees to the other layer. Metal plates or foils 7, 8,are then laid along the upper and lower surfaces respectively of thevwire construction to provide a sandwich effect. It will be noted thatwith the proper size of the wires 4, 5, and the proper curvature givento the wire 4, the plates 7, 8, will lie evenly along the upper andlower surfaces of the sandwich construction, touching the uppermosttangential position on each of the wires 4, 5, and also at the lowermosttangential positions. At these positions, in vertical lines coincidingwith an intersecting contact between wires 4 and 5, spot s welds orbrazed joints are effected as indicated at 11, 12,

13, these welds being in vertical alignment with one another so as tohold all parts of the structure rigidly in place. These welds may beprovided in any suitable and well-known manner, for example, by means ofa gang of short projecting welding electrodes positioned predetermineddistances apart, both longitudinally and transversely, according to thepoints of contact between each of the uppermost and lowermost surfacesof the wires and the contiguous portions of the plates 7, 8. Thecomposite length may also be received by welding rolls which serve tofuse the'metal at each point of contact by high frequencycurrent. TheWeld is performed by resistant heating and the technique employed isdetermined by the nature of the wires 4, 5, and the plates 7, 8. Ifdesired, a brazing etect can be used, as is well understood in the art.In one example, when properly carried out, three spot welds, or brazedjoints will have been provided in vertical line with one another at eachintersection of the wires 4 and rectilinear wires 5 and one spot weld orbrazed joint will have been provided as indicated at 14, at the positionwhere the uppermost surface of each wire 4 contacts the upper plate 7.Thus the plates are secured to the network of wires and the latter aresecured to one another by means of the joining process. And, one furtheradvantage resulting from the inter meshing arrangement is the absence oftwisting of the wires. Twisting atects the useful life of the wireinvolved.

The wires 4, 5, and the plates or' foils 7, 8, may take any diametraldimension and thickness, provided the straight wires are properly nestedwithin the troughs of the bent wires to present an even surface at theupper and lower faces thereof in order that the plates 7, 8, may liestrictly at. Heretofore, one of the major difficulties was in findingsuitable materials and to render them usable for the intended purpose.However, the present invention has discovered a way of economicallyproducing high strength metallic wire so as to bring it to a conditionsuitable for forming into an intermeshed wire network as described.Specifically, this invention contemplates the use of wires and strip ofprecipitation hardening stainless steel, alloy steels, titanium alloys,and mar-aging nickel steels. This latter steel for example, has a nickelcontent from about 6-18% by weight, and is readily procurable on themarket. It is noted for its high yield strength, up to about 350 k.s.i.,which is particularly important in the case of composites of smalloverall thickness, also for its relatively high ductilty, but moreespecially for its fracture toughness which is especially important incase the composite is to be used as an impact shield for militarypurposes. In addition, mar-aged steel has excellent weldability, withoutpost heat treatment, and may be readily formed to shape, which isimportant in the case of wire 4 that has to be bent to a particularpattern. I have obtained excellent results when constructing compositesof small thickness, approximately .030 inch overall, employing wire orfibers of 0.005 inch diameter and foils of approximately .010 inch.Composites, even of this minute thickness, have tremendous impact-energyabsorption and,

therefore, are suitable for light armor work, especially forconstituting the walls of a fuel tank, when used in conjunction with aself-sealing core structure, and may be positioned on a plane orhelicopter and subjected t small arms fire. However, it will beunderstood that the use of the composite is not restricted to themilitary iield, but in larger thicknesses and sizes may be used in theconstruction of railroad cars, large tonnage units for domestic andoverseas containerized shipping now coming into great'common usage,automobile bodies, truck bodies, small naval craft, also for oors,panels, prefabricated house panels, bathroom panels, vapor condensersand lubricating oil coolers, in fact, in any place where walls of lightweight but extremely tough construction, not easily distorted by suddenimpact, are required.

The high strength wire to be used herein may be processed by thefollowing steps:

(1) Select alloy rods, from the class of materials above described, onthe order of .062 inch diameter,

(2) Coat bundled rods with glassy silica to provide high temperaturelubrication,

(3) Heat the bundled rods to a temperature on the order of 1650-l850 F.by means of an induction heating coil,

(4) Pass the heated and coated rods through a die which may be carbideor alumina, to reduce same to about .010 inch diameter, or the reductionmay be continued to a final smaller size such as .003 inch,

(5) Optionally supplement the drawing by passing said reduced lwiresbetween high pressure rolls to form a flattened condition,

(6) Aging or stress-relieving the alloy at temperatures on the order ofabout SOO-900 F. for about one to four hours, or as may be required forthe respective alloys, and

(7) Subject the stress-relieved or aged Wire to shot peening to removeany remaining residual stresses.

While I do not wish to be limited to any theory as to why the improvedtruss core type of composite of the invention exhibits anextraordinarily high degree of irnpact absorption, I believe it is onaccount of the fact that any impact that strikes the upper plate 7 atzero obliqueness, indicated by the arrowed line C in FIG. 2, causes thestress to be divided along the 45 degree angle downwardly along the axisA, B, in both directions through the wire 4 and thus place the metal ofthe wire in both directions under compression. The compressive strengthyof the high strength alloys contemplated herein, particularly whenmar-aged steel is used, is enormous so that the impact force is absorbedwithin the upwardly and downwardly curved portions of the wire assumingthat the point of impact is applied at the position of the weld 14.While the optimum strength presented by the wire core is obtained whenthe ascending and descending portions of the wire 14 are positionedapproximately 45 degrees, it will be understood that correspondinglyenhanced strength is obtainable at angles greater than or less than the45 degree optimum.

The 'impace resistance of the composite is also enhanced by the factthat the plates 7, 8, are spaced from one another by the interveningtruss work. The separation of plates with high strength alloy mesh,which alloys possess a yield strength in excess of 200 k.s.i., alsocauses deection and tumbling by projectiles, thus reducing thepenetrative capacity while absorbing energy. It is well known that twoplates -separated from another offer a greater resistance topenetration, for example by a bullet or meteoroid, than would be thecase if the two plates were in close contiguous relationship or evenintegral with one another. Consequently, the high strength wire core ofthe composite serves not only to absorb the force of the impact bydividing thisforce into two directions at right angles to one another asexplained above, but also affects deiiection and disintegration ofcracked penetrating projectiles. Structures of the type described areparticularly beneficial for the holds of ships where the latter are aptto strike obstructions and require complete freedom from distortion ofshape, assuming that the various parts of the composite are made of theproper dimension and sizes as would provide the necessary overallthickness of hull. For reasons and by techniques to be explainedhereinafter, the composite may include a selfseallng material toeliminate any leakage caused by small punctures.

A further and final feature contemplated herein to enhance theprotective natur'e of the composite lies in the use of high strengthmetallic plates of varying hardness and ductility. For example, theupper or outer plate against which the projectile is directed shouldcomprise a metallic alloy of the type'described having a hardness on theorder of Rc 55-60. This will aid in causing the armor piercingprojectiles tocrack when impacting at velocities as high as 2800 f.p.s.On the other hand, the

bottom or lower plate should comprise a more ductile grade of metalwhose hardness may vary from -20 Rc. By sacrificing hardness for thelatter plate, maximum toughness is realized without a material loss instrength. Therefore, any broken pieces of projectile which may reach thelower plate'with u'nspent energy can only result in a detent ordeflection, but not a serious crack Aresulting in the possibledestruction of the composite.

The walls of freight'cars which are subjected to considerable interiorand exterior stresses from the heavy and cumbersome loads that ltheycarry, could advan tageously use composites of the type described inview of their lesser immunity from distortion upon impact and toughnessof the plates 7, 8. Indeed, where large plastic objects require metalreinforcement-members, applying thereto the improved structure wouldhave' particular beneficial effect provided that the empty spaces in thewire mesh are maintained and not filled with plastic so that thestructure could, without impediment, absorb the force of impact thatmight be applied to the exterior of the plastic body.

In FIG. 4, I have shown the manner in which two conposites can beassociated with one another and'fspot welded if desired at the variousmetal contacting surfaces.

This embodiment represents one way of providing for a multi-layercomposite. It will become evident from the description hereinafter thatother multi-layer composites are contemplated. In any event, thesecontacting ,surfaces indicated at 16, 17, 18, 19, may be spot welded inthe same manner as was explained in connection with FIG.

l 2, i.e. by the use of a gang electrode or by welding rollers,

using the resistance or thermal form of weld. The double composite shownin FIG. 4 can, of course, be multiplied into three, four or morecomposite units within the capacity of the welding machine, provided agreater overall thickness of the composite structure is desired, withouthaving to increase the size of the wires of the mesh or the thickness ofthe plates or foils.

In FIGS. 5 and 6, I have shown a modified structure of the improvedcomposite in that the wires 20, 21, are each given a bent or acurvilinear shape with reoccurring troughs and crests so arranged thatthe crests of one set of wires can rest in the troughs of the other setwhich are positioned at right angles to the first set. Thus, the wiresin these figures have an interwoven effect as shown more clearly in FIG.6in which one wire, for example, will pass over the trough of the nextwire arranged at right angles thereto and then under the crest of stillthe next wire, etc., so that a woven mat is simulated. Actually, themesh is formed by welding and not weaving. Insofar as the wires 20, 21are of the same size and assuming that the bending effect has beenpredetermined and carefully accomplished, the upper and lower surfacesof the interwoven mat are sufficiently level to receive the plate orfoils 22, 23. Spot welding can be provided at all the contact pointsbetween the wire core and the inside surfaces of the plates 22, 23, asindicated by the dots 24 so that the structure as a whole becomesintegral and selfsupporting. This structure can be used for manypurposes such as a wall. It may be made with an overall thickness assmall as .030 inch in which case the plate 22 actually becomes a foil.010 inch thick and the Wires are approximately .010 inch in diameter sothe latter are more properly termed metallic fibers. On the other, thewires 20, 21, can be of quite considerable diameter and the plate 22 ofheavy thickness to make up a composite of con- FIG. 2 in regard tospacing the upper from the lower plate by means of the wire core isstill present in the structure of FIG. 5 so that the latter reacts insuch a way as to make it difficult for a bullet or meteroid, forexample, to pass each of the plates when using the high strengthmetallic alloys having yield strengths in excess of 200 k.s.i., and ashigh as 350 to 400 k.s.i.

FIG. 7 shows still another form that the improved composite may take. Inthis figure, the wires 2S preferably all of the same size are laidcrosswise in spaced relation on the lower layer 26 of the wires, alsoequally spaced from one another. The plates 27, 28 are next laid on thetop of the wires 25 and also against the lower surfaces of the wires 26,sandwich fashion, and spot welds indicated at 29 are provided throughoutthe entire area of each of the plates 27, 28, at the places where all ofthe various metal elements contact one another so that metal Wires 25,26 are held securely in place not only with respect to one another butalso with respect to the plates. This modification, as in the case ofthose shown in FIGS. 2 and 5, may be made as thick'or as thin as desireddepending on its use, the changes being Imade in the sizes of the Wiresor rods 25, 26 and also the thickness of the plates27, 28. Thismodification also has the same advantage as was pointed out inconnection with FIGS. 2 and 5 in presenting two plates 27, 28 spacedapart, to offer increased resistance to the impact effects of a bullet.Any tendency of the upper plate 27 to move with respect to plate 28 inany planar direction, is resisted by the spot welds holding the variousparts together. Notwithstanding the fact that the wires 25, 26, are notanchored in the trough of the adjacent wires as indicated in FIGS. 2 and5, nevertheless, it has been found that the spot or line weld providedat every contacting point is sufficient completely to prevent the platesfrom moving in a planar direction with respect to one another. Thestructure, as a whole, is extremely rugged and is relatively inexpensiveto make.

In FIGS. 8, 9, I have shown still another form that the metal trusspositioned between two plates may take and in which the hollow spacesbetween the parts of the truss work can be filled with material,generally indicated at 29', that automatic self-seals in the event oneor both of the plates should *be fractured by a bullet or meteoroid.

Referring particularly to FIG. 8, the sandwich or interleaved positionof the composite is formed of a series of angularly shaped strips orribs indicated at 30 in which the sides of the strips or ribs have apredetermined inclination such as to leave at the top a flat portion 31and a similarly shaped portion 32 at the bottom. Thus the strip elementas a'whole can be characterized as having a zigzag formation extendingthe entire length of the composite and made of high strength alloy stripsuch as disclosed herein. There is a lower plate indicated at 33extending along the lower surface of the portion 32 and spot orlinewelded or brazed to the latter in any suitable manner as indicatedat 34. While, if desired, a similar plate may extend over the upperportion 31 of the ribs and be spot or line welded, I prefer that thetop, particularly in case the composite is to be used as a self-sealingfuel or gasoline tank be made of a multi-layer cloth material 35 whichmay be aluminized for heat defiection. Some suitable cloth materials arethe ones sold under the names Nomex and Daeron sold by the Du PontCompany. The cloth layers and/or cloth and plastic film may be securedto the upper portion of the strip or ribs by a layer 35 of 7 siliconeresin, vinyl-epoxy, epoxy-elastomer, .thermoplastic resin of 175 C. M.P.or any other suitable adhesive.

The multi-layer of cloth or cloth with a plastic film mentioned abovehas particular characteristics as described hereinafter which lendsitself to the functions that take place within the composite when abullet, for example, strikes and perhaps punctures the outer plate 33 ofthe container. Within the spaces formed by the angular strips, I preferto insert materials indicated generally 36 which has the facility ofself-sealing. For example, this material may comprise a hydrogenatedrosin mixed with urethane grade castor oil, up to 50% in prepolymerstate, and containing fully dried chopped glass and blue asbestos fibersat 35% of volume in the .viscous rosin mix. The mixture may also containmultiple catalysts contained within plastic capsules, or fine glasstubes of a small diameter, which are filled to 90'95% capacity. Thecatalyst may take various forms such as toluenediisocyanate, triethylenediamine-Dabco (liquid in dipropylene glycol) as a 33.3% solution ordimethylethanolamine. As a further accelerator, dibutyl dilaurate orstannous octoate 1% of the total reactive solids may also be used toadvantage while 1.5% of the basic catalysts or more should be madeavailable in the encapsulations based upon the total weight of thesealing resinous material.

The plastic capsules or the iine glass tubes are of extremely thinconstruction so that when a bullet penetrates the outer wall 33 of theself-sealing fuel or gasoline tank, it may leave a jagged opening 36 andpass through the space between one of the angular ribs to emerge out atthe cloth-plastic member 35. The bullet or the metal fracture causedthereby will break a number of the tiny catalyst capsules under acrushing impact and the contents will react with the hydrogenated rosinand urethane grade castor-oil mixtures to form a pressurized jelly oreven a solid plug indicated at 37 which vjoins integrally with thecloth-plastic covering 35. This reaction evolves CO, gas whichpressurizes and foams the content to form a polyurethane which mayattain a tensile strength of 3807 p.s.i. within the mesh ribbed orcompartmentized section. The encapsulations may also be fabricated byusing cotton or other textile threads as carriers for the catalyst.These carriers may be fed into ne plastic tubing or glass tubing andthen cut to nominal lengths and sealed by any of the well known methods.

For maximum safety in sealing punctured fuel tanks, I prefer toprepressurize the soft sealant in tank wall with use of CO2 gas at 0.50p.s.i.g. to help olset-th'e hydraulic pressure caused by weight of fuel.

Consequently, the oil or gasoline located within the tank at the clothside is prevented from escaping past the composite wall on account ofthe jelly or plug material formed in the manner stated. It will befurther noted that while the cloth member 35 does not have a high impactstrength, certainly not as great as if this covering were made of a highstrength metal, nevertheless, it does offer high resistance to a movingbullet, particularly if multiple layers are employed, on account of thespaced relation between the cloth layers and the metal plate 33, asexplained above. Many slower moving bullets will therefore not be ableto penetrate the clothlayers, having passed through the metal layer 33and their rvelocity and energy having been reduced. But as to any holesthat are produced in the cloth-plastic layers, such holes areimmediately closed by the viscous plastic and the chemical reaction ofthev elements including the released catalysts of the mixture containedwithin the confines of the affected rib.

In the event a re is contemplated, such as by an incendiary bullet or anelectrical short circuiting, any exposure of flammables to theself-sealing components could be extinguished by reason of contact withthe chlorinated biphenyl or brominated compounds to the extent of 3-7%of the mixture in the castor-oil polyol.

Further, in the event it is desired to make self-sealing 8 tanks incylindrical form, the structure shown in FIG. 9 may be used toadvantage. In this case, the lower plate 38 is made perhaps a littlethinner than the first plate 33 in FIG. 8, and it is also corrugated soas to permit a peripheral expansion and thus allow the composite wall asa whole to assume any degree of curvature desired to form a cylindricaltank. The laminated cloth wall 35 or a cloth and plastic combination,will obviously contract to the desired shape. As indicated of thestructure shown in FIG. 10, the tank wall in FIG. 9 has the samefacility of self-sealing at the position of the cloth layers. Thisstructure has the same advantage of offering two surfaces i.e., themetal member 38 and the cloth layers 35 which together might serve toslow down a traveling bullet to such extent that the latter may not beable to emerge from the cloth layer or a nylon felt, or graphite libercomposite with nylon. In a situation where small cylindrical items areto be produced, concentric tubular members may be employed rather thanusing the larger sections such as discussed above.

In the former situation, it is obvious that the overall thicknessbetween the cloth or nylon felt layers and the lower plate can be madeof any desired dimension, even down as low as 1A; inch and the ribs canbe made extremely thin in like manner, and yet the composite as a wholeshows remarkable impact strength without adding much weight to the tankmade in the manner. These thicknesses and dimensions can of course bemultiplied many times as may be necessary and the component parts alsoincreased in thickness along with the viscous bered mixture content.Extraordinary strength to bullet impact exhibited by the component maybe described, as indicated at FIGS. 2 and 4, to the Yfact that the forceof impact is divided between two portions of the ribs 30 which aspointed out hereinabove are set at an angle to one another and withrespect to the lower plate 33. This angularity of position alsoincreases the resistance against movef ment of the plate 33 sidewisewith respect either to the cloth or nylon felt cover 35 or with respectto the other portions of the ribs. It is also apparent these ribs neednot be made of solid metal but may, if desired, be perforated or perhapsformed of fairly stiff mesh material so as to allow the mixture contentbetween the ribs including the released catalyst to move readily fromone space` to another without restriction so as to achieve a fasterreaction at the puncture opening that need be sealed. This is alsoenhanced bythe CO3 pressurization from the catalyzed polyol reactions.

A further and final embodiment is illustrated in FIG. 11. While thisstructure has utility independently of the other embodiment, it ispreferred when used in conjunction therewith. For convenience, thisimprovement has been illustrated with regard to the network structureshown in PIG. 5; however, the other variations are also applicable.

The intermeshed high strength metallic wires 40 and 41 are formed anddisposed as shown in FIG. 5 and welded to the lower plate 42. Tocomplete the composite structure, sintered graphite pellets of 94%carbon with 6% copper/ alumina 4% vol. as made by an aqueouscoprecipitation process or alumina pellets 43 or alternate layers ofboth are disposed between the network structure ofA wires 4.0 and 41 anda top plate 44. These high dense and compact pellets have been found topossess high hardness and good compressive strength. The graphite cermetpellets attain 7.5 k.s.i. to k.s.i. and the alumina 300 k.s.i. to 500k.s.i compressive strengths. These pellets, which have been foundparticularly effective in defeating armor piercing projectiles, may beprovided with a coatmg or cladding. One particularly suitable claddingis one composed of first layer of moly-manganese 2-3 mils, and a secondcoating of kcoating of moly-boride of about 10 y mils to 4520 Knoophardness. z

These pellets which may vary in diameter from -a small M3" diameter sizeup to '1A inch or 3A" diameter, are

bonded or sinteredA on'A to the. wire forms'or plates. The bonding maybe effected by a preferable void filling adhesive such asepoxy-elastomer withv 1.5% ceric oxide 45 or other heat curin'gresin.The latter maybe cured in situ by the application of electricfcurrent tothe wire network Y or electrical thermal conducting reinforcing fibers.In any case, an effective bonded composite results. In addition to thenon-metallic or cermet pellets, compacted sintered alloys of titanium,steel or aluminum with fibers may be used for the pellets. These alsomay be provided with a coating or cladding to enhance their propertiesto cause impactingprojectiles to crack, disintegrate, and/or tumble. Forexample titanium may be beryllided to about 1500 Knoop hardness, steelborided up to 4500 vKnoop and aluminum sintered 'with boron carbide toabout 1600 Knoop hardness.

It will be understood that this invention is susceptible to modificationin order to adapt it to different usages and conditions. For example, amultiple layer composite may be constructed using a combination of wiresdisposed at angles of 90 or less and/or pellet networks intermediate twoor more layers or plates, foils or non-metallic layers such as discussedherein. Accordingly, it is desired to comprehend such modificationswithin this invention as may fall within'the sc ope of the appendedclaims.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows: f

1. An impact resistant composite structure comprising at least onemetallic sheet presenting an outermost surface to the structure, and anetwork of separate individual wires stacked in unwoven layers, one laiddirectly on the other, an outer layer of which lies in a plane adjacentto said sheet, with the wires thereof in abutting engagement with saidsheet substantially the length thereof, said sheet and the wires of thelayers of said network being bonded directly together at contiguouspoints, the layers of said network comprising at least two layers eachof which includes a set of separate individual substantially parallelmetallic wires having yield strength at least about 200 k.s.i. and theindividual wires of one of said sets being disposed in angular relationto wires of the other of said sets, said wires being selected from thegroup consisting of precipitation hardening stainless steels, maragingnickel steels, alloy steels and titanium alloys.

2. An impact resistant composite structure according to claim 1characterized by wires in adjacent of said layers being bonded directlyto each other and the wires in one of said layers being bonded to saidsheet in points defining a plurality of connections within said networkin lines extending substantially perpendicular to said sheet.

3. AA impact resistant composite structure as set forth in claim 1characterized by said wires of respectively adjacent layers having bentportions forming offsets therein whereby to provide for nesting ofadjacent wires, one within the other where they cross.

4. An impact resistant composite structure comprising at least onemetallic sheet, and a network of wires stacked in unwoven layers, onelaid on the other, and outer layer of which lies in a plane adjacent tosaid sheet and in limited touching engagement therewith, said sheet andlayers of said network being bonded together at contiguous points, thelayers of said network comprising at least two layers each of whichincludes a set of substantially parallel metallic wires having yieldstrength at least about 200 k.s.i. and the wires of said sets beingdisposed in angular relation to one another, said wires being selectedfrom the group consisting of precipitation hardening stainless steels,mar-aging nickel steels, alloy steels and titanium alloys, the wires ofat least one said layer being bent to a sinusoidal form producing aregular series of crest and troughs therein, the wires in said one layernesting in their'troughs the wires of an adjacent layer and a secondsheet being disposed parallel to said first sheet with the vsaid networkherebetween.

5. The impact resistant composite structure according to claim 4including a layer of highly dense and compact v pellets in pointcontactwith wires of said network, said pellets being non-metallic and selectedfrom the group consisting of sintered graphite and alumina.

6. The impact resistant composite structure according to claim 4 andincluding a layer of highly dense, compact sintered pellets, saidpellets being selected from the group consisting of titanium, steel andaluminum.

7. An impact resistant composite structure comprising at least twovspaced apart sheets at least one of which is metallic and presents anoutermost surface to the cornposite structure and a network of wiresstacked in unwoven layers, one laid directly on th'e other, an outerlayer of which lies in a plane adjacent to said one sheet and in limitedtouching engagement therewith, said sheets and layers of said networkbeing bonded directly together at contiguous points, the layers of saidnetwork comprising at least two layers each of which includes a set ofsubstantially parallel metallic wires having yield strength at leastabout 200 k.s.i., said wires being selected from the group consisting ofprecipitation hardening stainless steels, mar-aging nickel steels, alloysteels and titanium alloys, and said two layers of said networkcomprising lirst and second sets of metallic wires wherein the wires ofthe respective sets are disposed at right angles to one another, saidwires contiguous to said sheets being bonded thereto at every point ofcontact therewith, and wires of respectively adjacent layers havingformed portions providing for nesting, one within the other where theycross.

8. The impact resistant composite structure according to claim 7 andincluding a layer of highly dense, compact sintered pellets, saidpellets being selected from the group consisting of titanium, steel andaluminum.

9. An impact resistant composite wall structure comprising protectivemeans in the form of outer sheets arranged in a substantially parallelspaced relation and a network of unwoven layers of separate individualmetallic wires, one layer stacked on the other, forming a core betweensaid sheets, at least an outer one of said layers having the wiresthereof presenting themselves to make line contacts with an outer one ofsaid sheets essentially the length thereof, the individual wires of eachlayer being in substantially parallel relation and the said respectivelayers having adjacent portions of their wires connected by being bondeddirectly to each other and to said sheets at points lying in a pluralityof generally straight lines extending at substantially right angles tosaid sheets, one said sheet being relatively hard and unyielding and theother having a capacity to bend and yield to the stress of impact.

10. An impact resistant composite structure comprising at least onemetallic sheet, and a network of wires stacked in unwoven layers, onelaid on the other, an outer layer of which lies in a plane adjacent tosaid sheet and in limited touching engagement therewith, said sheet andlayers of said network being bonded together at contiguous points, thelayers of said network comprising at least two layers each of whichincludes a set of Substantially parallel metallic wires having yieldstrength at least aboutA 200 k.s.i. and the wires of said sets beingdisposed inr angular relation to one another, said wires being selectedfrom the group consisting of precipitation hardening stainless steels,mar-aging nickel steels, alloy steels and titanium alloys, at least oneset of said parallel wires being bent in a uniform sinusoidal manner toform crests and troughs which occur respectively in coincidence With oneanother, the depths of said troughs being equal to the diameter of thewires in an adjacent of said sets, the wires in the said adjacent ofsaid sets being formed and arranged to nest in said troughs so as toposition portions of the outer surface thereof in a plane common withouter surface portions of said crests, said outer surface portions of atleast a portion of said wires being secured t0 said sheet. n

11. An impact resistant composite structure according to claim 10characterized by the crest portions of the wires of said one set havingtouching engagement with said sheet and said crest portions are formedin a manner that impacts sustained by said sheet are dispersed angular-1y into the composite structure.

12. A structure as set forth in claim 11 characterized by said crestportions forming substantially 45 angles.

13. A structure according to claim 11 characterized by a second sheet inopposing spaced relation to said one sheet having the troughs of saidwires of said one set in touching engagement therewith andv the touchingportions thereof bonded thereto whereby said dispersed impacts areabsorbed in a compressive stress of wires in a sense longitudinallythereof.

14. A structure according to claim 13 characterized by the wires of eachset being bent in a sinusoidal fashion to form a regular series ofcrests and troughs therein to respectively nest portions of the crestsand troughs of wires in adjacent sets, overlapping wires being formedthereby and bonded together at said crests and troughs to define aplurality of bonded connections extending between said sheets in linessubstantially perpendicular thereto.

References Cited UNITED STATES PATENTS 745,547 12/1903 Wight 52-723X2,049,246 7/1936 Brown 252-477 R X 12 2/ 1910 Swinscoe 52-660 7/ 1912Hansbrough 52-660 X 12/1913 Wellen '----12 52-662 3/ 1914 Lachman A52-660 X 9/ 1921 Freyssinet 529-662 10/1924V Holmgreen 52-660 X 3/ 1925Rogers 52-660 12/ 1929 Birdsex et al 52-660 3/ 1943 Reed 524-660 X6/1959 Leuthesser 52-660 X 5/1961 Crooks 52-66() X 3/1910 `Cowper-Coles114-12 5/1915 Potterv 139-425 RX 5/ 1925 Pfersdortf 109--182 X 11/ 1948Wallace 29-19I.2 X 5/ 1954 Pitman 29-191.4 X 1/ 1956 Meyer 89-36 A X 12/1958 Flanagan 29-195 X 9/1962 Juras 29-183 X 6/1964 Mote, Jr., et al.29-183 X t 10/ 1965 Rhudy 29-183 4/1966 Rogers 117--100 B X FOREIGNPATENTS 6/1949 Canada 52-664 10/1958 Australia 52-664 11/ 1964 France52-664 ALLEN B. CURTIS, Primary Examiner UNITED STATES PATENT OFFICECERTIFICATE OF .CORRECTION Patent No. 3.764.277 Dated october 9. 1973nventods) Russell E. Hollis It 4is certified that error appears in theabove-identified patent and that said Letters Patent are herebycorrected as shown below:

Col. l, line 60,A "interventing" is amended to read signedand sealedthis 11th day of June 1971;.

(SEAL)l Attest:

EDWARD M.FI.ETCHER,JR. a c. MARSHALL DANNv Attesting OfficerCommissioner of Patents nqnnnnnnc 50316-5569 UNITED STATES PATENT OFFICECERTIFICATE 0F yCORRECTION Patent No. 3 ,764,277 Peted october 9, 1973Inventods) Russell E. Hollis It is certified that error appears in theabove-identified patent and that said Letters Patent are herebycorrected as shown below:

Col. l, lne"60, "interventing" is amended to read intervenincr line 50,impace" is corrected to read impact Col. 5, line 16., "detent" iscorrected to read dent Signed and sealed this 11th day of June (SEAL)Attest:

EDWARD M.FLETCHER,JR. C. MARSHALL DANN Attestng Officer Commissioner of'Patents RM P0-1050 (1Q-69) USCOMM-DC 60376-P69 t u.s. GOVERNMENTPRINTING OFFICE z 1969 o-s66sl4,

